As a warehouse worker in the Inland Empire, the nation's biggest distribution hub for consumer goods, Jorge Soto handles shipments for retail giant Walmart every day.

But Soto, who works for a subcontractor, claims that along with routine jobs such as unloading trucks, he also has been ordered to perform an illegal task: falsifying employees' time sheets to cheat them out of getting the minimum wage.

The Mexican-born Soto, 47, said in a sworn court statement that his supervisors forced him, when he was the lead member of his crew, to severely understate workers' hours. He said the purpose was to cover up the widespread practice of paying well below the legal minimum, which is $8 an hour in California.

As Soto explained in an interview, "they wanted to wash their hands of it through me," adding that workers sometimes received as little as $3 or $4 an hour.

A suit filed in federal court in Los Angeles on behalf of Soto and dozens of other warehouse workers charges three companies that handle Walmart goods with fraudulent pay practices. The case, along with recent investigations by state labor officials that have led to proposed fines of close to $1.4 million, depict what critics say is the underside of the vast warehouse business in the region.

An economic juggernaut that employs about 100,000 people, the Inland Empire warehouses are a staging point for Apple computers, Gerber baby clothes, Polo apparel and other brand-name imports.

They handle goods from Asia that come through the ports of Los Angeles and Long Beach, to be distributed around the U.S.

According to court documents and interviews with workers:

Crew leaders such as Soto were under orders at some warehouses to force workers to sign blank time sheets, a tactic that made it easier to cheat employees out of their rightful pay.

Workers often were paid only for the time they spent loading and unloading trucks - not for the time they put in sweeping warehouses, labeling and restacking boxes or waiting to find out if they would be assigned work.

High heat in the warehouses and constant pressure for speed created safety problems. These and other issues triggered an investigation that led the California Division of Occupational Safety and Health, or Cal/OSHA, in January to accuse four warehouses of more than 60 workplace safety violations and to seek $256,445 in penalties.

Many workers, classified as temporaries despite years of service, said they were threatened with being blackballed and never being hired again if they raised questions about their pay or took part in protest or unionizing efforts. Labor leaders, who announced plans in 2007 to recruit the warehouse employees, say that the intimidation and perpetual job insecurity are key reasons why their "Warehouse Workers United" campaign has failed to unionize any workers.

Workers also were subjected to other indignities, such as being forced to pay $1 per week to rent a shirt with a company logo, and being required to show up every day, only to be sent home some days for lack of work.